This invention relates to a hydraulic torque impulse generator of the type having a drive member connected to a rotation motor and including a cylindrical fluid chamber defined by a circumferential wall and two end walls, an output spindle rotatably supported in a coaxial relationship with the drive member and having a rear portion extending into the fluid chamber, which spindle portion has at least one radial slot each supporting a radially movable seal element for sealing cooperation with seal lands on the circumferential fluid chamber wall, and first seal ridges on the rear spindle portion for sealing cooperation with second seal ridges on the circumferential fluid chamber wall, for dividing the fluid chamber into at least one high pressure compartment and at least one low pressure compartment during short intervals of the relative rotation between the drive member and the output spindle.
In hydraulic torque impulse generators of the above type there is a problem both to have a good sealing action between the rear spindle portion, inclusive of the seal elements, and the fluid chamber end walls during impulse generation and to have a low friction relative rotation between the drive member and the rear spindle portion between each impulse generating phase. If very small clearances are used, between the ends of the rear spindle portion and the end walls of the fluid chamber, a good tightness is obtained, which would result in high peak pressures. Unfortunately, the small clearances also means a very thin fluid film between the moving parts, which causes a high viscous friction and a slow acceleration of the drive member relative to the output spindle before each impulse generating phase. The result is not an increased power output of the impulse generator, because the energy in each torque impulse depends not only on the tightness of the fluid chamber compartments but also on the relative speed of the drive member and the output spindle. A slow acceleration of the drive member also means a low impulse rate.
The object of the invention is to accomplish an improved power output of a torque impulse generator of the above type by combining a good tightness of the fluid chamber compartments during the impulse generating phase and a low friction acceleration phase.